In the medical field, observation and diagnosis of an internal organ in a body cavity with the use of medical equipment having an image-capturing function, such as X-ray, CT and MRI apparatuses, an ultrasonic observation apparatus and an endoscope apparatus, are widely performed.
For example in the case of an endoscope apparatus, a long and thin insertion section is inserted into a body cavity; an image of the internal organ in the body cavity acquired by an objective optical system provided for the tip of the insertion section is captured by image-capturing means such as a solid-state image capturing device; and an endoscope image of the internal organ in the body cavity is displayed on the monitor screen based on the image-capturing signal. An operator performs observation and diagnosis based on the endoscope image displayed on the monitor screen.
Since the endoscope apparatus is capable of directly capturing an image of digestive tract mucous membrane, the operator can observe various findings such as the color tone of mucous membrane, the shape of a lesion shape and a fine structure on the surface of mucous membrane.
Recently, a capsule endoscope apparatus has been developed as medical equipment having a new image-capturing function, the usefulness of which can be expected similarly to the endoscope apparatus. The capsule endoscope apparatus captures images of the inside of a body cavity after a subject to be examined swallows a capsule endoscope until it is discharged to the outside of the body and sends image-capturing signals to a receiver provided outside the body. As many as several hours are required for the capsule endoscope to pass through each of digest tracts of esophagus, stomach, duodenum, small intestine and large intestine inside the body cavity and be discharged to the outside of the body, after the subject to be examined swallows the capsule endoscope.
Assuming that if the capsule endoscope apparatus captures, e.g., 2 (frames of) images per second and sends the images to the receiver outside the body, then it takes 6 hours from the capsule endoscope apparatus being swallowed to being discharged outside of the body, the capsule endoscope apparatus would capture as many as 43200 pieces of images while advancing in through the body cavity.
Displaying all of the large number of images on an observation apparatus to perform observation and diagnosis would take 72 minutes, a relatively long period of time, even if, e.g., ten images are displayed per second. Accordingly, a surgeon to observe the captured images for such length of time would be quite problematically subject to a high burden of time.
In addition, final diagnosis in endoscopy using a capsule endoscope apparatus or a typical endoscope apparatus largely relied on the subjectivity of a doctor, thus problematically causing fluctuation in the diagnosis quality. For this reason, to improve the quality of image diagnosis and reduce the time for shadow-reading an endoscope-image, it has been expected to realize computer-aided diagnosis (CAD) that allows for automatically detecting from an endoscope image a presence of a lesion such as hemorrhage, reddening, abnormal blood vessel and polyp.
Computer-aided diagnosis (CAD) is realized by an endoscope diagnosis supporting apparatus. The endoscope diagnosis supporting apparatus provides objective and numerical diagnosis assistance by presenting a doctor with whether or not an image to be diagnosed is categorized in such observations by using threshold processing or a statistical or instatistical identification apparatus using various characteristics amounts calculated from a region of interest (ROI) in an image. Also, the endoscope diagnosis supporting apparatus reduces the burden of the doctor in shadow-reading, by selecting and presenting an image doubted to include a lesion.
Meanwhile, several approaches have been used to detect hemorrhage which can be caused by various pathological reasons. One of such approaches is presented in the publication of the PCT WO 02/073507 A2 which proposes a method for automatically detecting hemorrhage based on hue, saturation, and brightness of an observation target area in an endoscope image, using the above-described endoscope diagnosis supporting apparatus.
However, in the method described in the publication, the hue, saturation, and brightness values of the observation target area are compared with hue, saturation, and brightness sample values of a normal mucosa which are preset in the endoscope diagnosis supporting apparatus, and then it is determined whether the observation target area is a normal mucosa or a hemorrhage portion by means of diversion from the sample values.
Thus, there was a problem that the determination results depended on the sample values preset in the endoscope diagnosis supporting apparatus.
Therefore, the present invention aims to provide an image processing apparatus, an image processing method, and an image processing program capable of detecting a hemorrhage area by using an amount of change in an image signal or a color signal in an outline part of a bloody area.